The present invention generally relates to an electronic assembly and, more particularly, to an electronic assembly having a multilayer adhesive structure.
In the recent development of integrated circuit (IC) chip mounting technologies, an IC chip may be bonded to an electronic substrate by establishing electrical communication between conductive bumps built on the IC chip and bond pads provided on the electronic substrate. When such bonding technique is used, an anisotropic conductive film (ACF) may be provided between the IC chip and the electronic substrate such that electrically conductive particles embedded in the ACF provide such electrical communication.
Referring initially to FIGS. 1A-1C, a process for bonding a microelectronic structure 10 to an electronic substrate 20 is shown. The microelectronic structure 10 may be provided with multiple, electrically-conductive bumps 12 formed on a top surface for providing electrical communication to microelectronic circuits (not shown) in the microelectronic structure 10. Each of the conductive bumps 12 may be built on a bond pad 14 and a seed layer 16, and may be insulated by a dielectric layer 18. The electronic substrate 20 may be provided with multiple bond pads 22 formed on a top surface 24. The electronic substrate 20 may include but is limited to one of a printed circuit board (PCB), silicon (Si) substrate and glass substrate. An anisotropic conductive film (ACF) 30, which may include multiple, electrically-conductive particles 32 embedded in an electrically-insulating material 34, may be applied over the top surface 24 of the electronic substrate 20.
The microelectronic structure 10, the electronic substrate 20 and the ACF 30 may be placed in a heat-bonding equipment, where a suitable pressure may be applied to press the microelectronic structure 10 against the electronic substrate 20, resulting in an electronic assembly 40 as shown in FIG. 1C. Referring to FIG. 1C, electrical communication between the microelectronic structure 10 and the electronic substrate 20 may be established by electrically-conductive particles 32a, 32b and 32c, which provide electrical conductance between the conductive bumps 12 and the bond pads 22.
The bonding process using ACF may be cost efficient. However, it may be difficult to control the distribution of the electrically-conductive particles 32 when an ACF is prepared. As a result, referring to FIG. 1D, a number of the electrically-conductive particles 32d may cluster between adjacent conductive bumps 12 and thus cause undesirable short-circuiting therebetween, which may damage the normal circuit function. To address the issue, ACF films with a controllable pattern of distribution of electrically-conductive particles have been proposed. However, such ACF films may be too expensive to be used in general bonding processes.